A Moloney murine sarcoma virus (MSV) specific p60 polypeptide containing murine group p30 and p15E antigenic determinants, is also phosphorylated. Both virion and cellular p60 are labeled with P32 as is virion P12. P60 also binds to single-stranded but not double-stranded nucleic acids. Purified endonuclease restriction (endo R) Eco Rl fragments of herpes simplex virus type 1 (HSV-1) DNA have been used successfully to transform mouse Balb 3T3 cells. End terminal HSV-1 Eco Rl fragments are altered in size and amount in syncytial plaque morphology variants of HSV-1 suggesting a host-cell influence.